During the UAE Tour, Thomas De Gendt encountered a mechanical issue. After the race, Adam Hansen criticized the hookless rim system, sparking widespread skepticism among road cyclists about using hookless rims. Although the system is reliable and has been thoroughly tested by the brand, there are certain safety considerations and precautions to keep in mind when using hookless rims.
The introduction of hookless rims has brought a fresh perspective to the development of road bike rims. A few years ago, racing tubular rims were nearly perfect in terms of lightweight, aerodynamics, and rigidity, but it seemed like their development had stagnated. Later, brands' commitment to tubeless systems gradually replaced traditional tubular rims, making the design of carbon rims more complex. This includes the arrangement of carbon fibers and the materials and resins used, which has led to an increase in the average weight of rims in recent years instead of a decrease.
Although brands have made the rims lighter by improving the quality of carbon fiber and resins, the design of hookless rims has simplified the manufacturing and lamination process. Unlike traditional rims that use a bead hook to secure the tire, hookless rims rely on air pressure to press the tire tightly onto the rim, which has made manufacturing simpler. As a result, manufacturers no longer need to reinforce the rim's fixation areas as much, allowing them to produce lighter, more durable, and more affordable rims.
However, there are some issues with hookless rims during use. The first is the dimensional tolerance problem between the tire and rim, which is particularly crucial for hookless rims since they lack the structure to secure the rubber.
When choosing tires for our hookless rims, we must select a model that is fully compatible with the rim. To help with this, rim manufacturers usually provide a list of tested and guaranteed compatible tire models. While being limited to certain tire models might be inconvenient, safety should always be the top priority.
When it comes to compatibility, the size of the tire is crucial. The internal width of a hookless rim is usually no less than 23mm, which means the smallest tire size we can install is 700x28c, and this is non-negotiable. A 25mm tire cannot fully support the rim's edge, which could lead to the tire coming off.
Another important factor when using hookless rims is tire pressure. While inflating large volume tubeless tires to 8 bar (about 120 psi) was once the norm, the limit is lower on hookless rims, typically set at 5 bar (about 70 psi). This pressure might seem low, but we need to consider that we’re using 28mm tires, which naturally require lower inflation pressure compared to 25mm tires. Moreover, we should break the traditional belief that higher pressure improves rolling performance, as recent studies have proven the opposite. Wider tires with appropriate pressure provide a perfect balance between cushioning, rolling quality, and grip, whether during acceleration or cornering.
To minimize the use of tools when installing the tire, we first use our hands to insert one side of the tire into the central groove of the rim, pushing it in as deep as possible to create space for the second side. Then, we place the second side into the central groove as well. If we have to use tire levers, that's okay too, since we don’t need to worry about puncturing the inner tube. The goal is to create an initial seal so that air can reach all around the tire while pushing the sidewalls into their final position.
If the tire is new, we can try inflating it with a regular pump. When installing, removing the valve core can help the airflow be smoother, which is always helpful. However, for hookless rims, the initial inflation process can be a bit more complicated, so using a compressor is more convenient. Another tip to simplify the process is to spray some soapy water on the tire sidewalls.
At this point, it’s recommended not to add sealant immediately but to install the tire first. This ensures the valve and sidewalls are properly sealed against the rim. During the first inflation, we set the pressure close to the maximum allowed value to ensure a perfect fit and check the evenness of the seal around the tire by looking at the bead line on the sidewall. All tubeless tires have this bead line.
Finally, we inject the sealant through the valve using a syringe, then inflate the tire to the normal operating pressure. At this point, we can move the wheel in different directions to ensure the sealant covers every corner. For better sealing, it’s recommended to ride the bike immediately after inflating, just a few kilometers is enough to allow the sealant to distribute evenly inside the tire.
Another important point to note is that for tubeless systems, if a puncture occurs that the sealant can't fix, you can use an inner tube. However, the inner tube should only be used when absolutely necessary, such as when you need to get home, and to maintain the same air pressure as the original tubeless tire. This comes with the risk of another puncture due to impacts with the rim. After the ride, the inner tube should not be used any longer, as it usually prevents the tire from seating properly, which could lead to the tire coming off next time. As the saying goes, "a lid for every pot," tubeless tires and hookless rims are the perfect match.
Recommended readings
- Beginner's Guide: 8 Steps to Wrap the Perfect Bar Tape
- 11 High-Performance Carbon Fiber Wheelsets Face-Off: Part 4
- 11 High-Performance Carbon Fiber Wheelsets Face-Off: Part 3
- 11 High-Performance Carbon Fiber Wheelsets Face-Off: Part 2
- 650B vs 700C Wheelset
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